Determining a minimum state of charge for an energy storage means of a vehicle

ABSTRACT

A method for determining a minimum state of charge for an energy storage means of a vehicle can include: determining a routine of use of charge of the energy storage means; determining a user requirement for future driving of the vehicle; predicting a reduction in the state of charge of the energy storage means associated with the user requirement in dependence on the determined routine; determining a minimum state of charge for the energy storage means for enabling the user requirement to be satisfied in dependence on the predicted reduction; and providing an output to the user indicative of a time requirement for increasing the state of charge of the energy storage means to a value at or above the minimum state of charge.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of GB PatentApplication No. 1718717.0 filed Nov. 13, 2017, the content of which isincorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to determining a minimum state of chargefor an energy storage means of a vehicle. In particular, but notexclusively it relates to determining a minimum state of charge for anenergy storage means of an electric vehicle.

Aspects of the invention relate to a method, a controller, a vehiclesystem, a vehicle and a computer program.

BACKGROUND

It is known for a vehicle (e.g. electric vehicle) to comprise an energystorage means (e.g. traction battery) which takes several hours to befully charged from a depleted state.

Some electric vehicles have traction batteries that provide relativelylow vehicle ranges as compared to internal combustion engine (ICE)powered vehicles, and can only charge at a relatively slow rate, takingseveral hours to fully charge. The charging infrastructure in some areasis scarce compared to petrol/gasoline or diesel fueling infrastructure.These issues can create range anxiety among electric vehicle users,compounded by a strong incentive to only charge at home or at workrather than in the middle of a journey, for example.

One issue with such vehicle is that a user stranded at an inconvenientlocation such as a service station with insufficient charge forachieving a goal, may not know how long they will need to charge theirvehicle for in order to provide sufficient charge. Consequently, theymay wait longer than is strictly required while their vehicle is fullycharged.

It is therefore an aim of an embodiment/embodiments of the presentinvention to overcome or at least partially mitigate problems associatedwith the prior art.

SUMMARY

According to an aspect of the present invention, there is provided amethod for determining a minimum state of charge for an energy storagemeans of a vehicle, the method comprising: determining a routine of useof charge of the energy storage means; determining a user requirementfor future driving of the vehicle; predicting a reduction in the stateof charge of the energy storage means associated with the userrequirement in dependence on the determined routine; determining aminimum state of charge for the energy storage means for enabling theuser requirement to be satisfied in dependence on the predictedreduction; and providing an output to the user indicative of a timerequirement for increasing the state of charge of the energy storagemeans to a value at or above the minimum state of charge.

This provides the advantage of reducing range anxiety, because themethod learns the users personalized routine energy needs, to inform theuser how long the vehicle will need to charge for, as a minimum, inorder to satisfy the user's driving requirements.

In some examples, the user requirement defines a time period and/ordistance of future driving of the vehicle for which the energy storagemeans must not be in a charge-depleted state. In some examples, the userrequirement defines one or more of: a location (e.g. destination); adistance; and a time period. In some examples, the method comprisesdetermining a rate of charge associated with a charger for the energystorage means, and determining the time requirement in dependence on thedetermined rate of charge.

This provides the advantage of a greater degree of accuracy fordetermining the user's energy needs.

In some examples, the time requirement is indicative of a time at whichor how long until the state of charge of the energy storage means isexpected to be at the value. In some examples, the time requirement isindicative of when the state of charge of the energy storage means isexpected to transition from being below the value to being at the value.In some examples, the method comprises: charging the energy storagemeans to the value, in dependence on receiving a user confirmationinput.

This provides the advantage that the user is provided with personalizedinformation indicating a minimum charging time for the vehicle.

In some examples, the method comprises determining a second userrequirement for future driving of the vehicle, and for the second userrequirement: predicting a reduction in the state of charge of the energystorage means associated with the second user requirement in dependenceon the determined routine; determining a second minimum state of chargefor the energy storage means for enabling the second user requirement tobe satisfied in dependence on the predicted reduction; and providing asecond output to the user indicative of a time required for increasingthe state of charge of the energy storage means to a value at or abovethe second minimum state of charge, wherein the output and the secondoutput are provided together and are each user-selectable, enablingcharging of the energy storage means to the corresponding value to beperformed when selected. In some examples, the method comprisesproviding a required state of charge output prompting the user to inputa value of a required state of charge of the energy storage means,wherein the required state of charge output and the output are providedtogether and are each user-selectable, enabling charging of the energystorage means to the corresponding value to be performed when selected.

It will be appreciated that a vehicle traction battery, or other energystorage means, may be charged or recharged by being electrically coupledto a charging station. This may be achieved by either the vehicle inwhich the battery is installed, or the battery itself, being pluggedinto the charging station using a suitable electrical cable, or by beingelectrically coupled via an inductive charging circuit as are both knownin the art.

This provides the advantage of presenting the user with personalisedpre-charging options, enabling the user to select a charging option, andtherefore charging time, that best matches the user's intentions.

In some examples, the output is provided while the vehicle is plugged inor otherwise coupled to a charging station. In some examples, the outputis provided in dependence on detection of the vehicle being plugged inor otherwise coupled to a charging station. In some examples, the outputis provided in response to a determination that the predicted reductionsubtracted from a current state of charge of the energy storage meansindicates that the energy storage means would be in a charge-depletedstate.

This provides the advantage that the user is prompted to charge theirvehicle when appropriate. Additionally, a user relying on this promptingwill avoid charging the battery unnecessarily, saving cost, time andextending the battery service life.

In some examples, the output comprises a post-charging messageindicating that the state of charge of the energy storage means is atthe value. In some examples, the output comprises a post-chargingmessage indicating that the state of charge of the energy storage meanshas transitioned from being below the value to being at the value.

This provides the advantage of reducing unnecessary waiting on the partof the user.

In some examples, the routine is determined using measurements of thestate of charge of the energy storage means recorded with respect to acyclic calendar-based time interval.

This provides the advantage of a greater degree of accuracy fordetermining the user's energy needs, because the user of the vehicle ismostly likely to follow a cyclic calendar-based driving routine, e.g.similar commuting patterns from week to week.

According to a further aspect of the invention there is provided amethod for determining a minimum charge for an electric or hybridelectric vehicle, the method comprising: determining a routine ofelectrical discharge for driving the vehicle under electric power;determining a destination for the vehicle; predicting expectedelectrical discharge for driving the vehicle under electric power forreaching the destination from a current location of the vehicle independence on the routine; and while the vehicle has insufficient chargeto reach the destination, causing, at least in part, an output to beprovided to the user dependent upon a minimum charge for enabling thevehicle to be provided with enough charge to reach the destinationassuming the predicted expected electrical discharge.

According to a further aspect of the invention there is provided amethod for determining a minimum state of charge for an energy storagemeans of a vehicle, the method comprising: determining a routine of useof charge of the energy storage means; determining a user requirementfor future driving of the vehicle; predicting a reduction in the stateof charge of the energy storage means associated with the userrequirement in dependence on the determined routine; and determining aminimum state of charge for the energy storage means for enabling theuser requirement to be satisfied in dependence on the predictedreduction.

According to another aspect of the invention there is provided acontroller comprising means for carrying out any one or more of themethods described herein. The means may comprise: at least oneelectronic processor; and at least one electronic memory deviceelectrically coupled to the electronic processor and having instructionsstored therein, the at least one electronic memory device and theinstructions configured to, with the at least one electronic processor,cause a vehicle system at least to perform any one or more of themethods described herein.

According to an aspect of the invention there is provided a controllerfor determining a charging requirement for an energy storage means of avehicle, the controller comprising:

-   -   input means for receiving data indicative of a use of charge of        the energy storage means;    -   processing means configured to:        -   determine a routine of use of charge of the energy storage            means;        -   determine a user requirement for future driving of the            vehicle;            -   predict a reduction in the state of charge of the energy                storage means associated with the user requirement in                dependence on the determined routine;            -   determine a minimum state of charge for the energy                storage means for enabling the user requirement to be                satisfied in dependence on the predicted reduction; and    -   output means for providing an output to the user indicative of a        time requirement for increasing the state of charge of the        energy storage means to a value at or above the determined        minimum state of charge. The input means may comprise an input        device. The processing means may comprise at least one        electronic processor. The output means may comprise an output        device.

According to a further aspect of the invention there is provided avehicle system comprising the controller according to any precedingaspect of the invention, and at least one output device, wherein theoutput device is configured to receive the provided output, and topresent the output to a user.

According to a further aspect of the present invention there is provideda vehicle comprising the controller or the vehicle system according toany preceding aspect of the invention.

According to a further aspect of the present invention there is provideda computer program that, when run on at least one electronic processor,causes a controller according to any preceding aspect of the inventionto perform any one or more of the methods described herein.

Within the scope of this application it is expressly intended that thevarious aspects, embodiments, examples and alternatives set out in thepreceding paragraphs, in the claims and/or in the following descriptionand drawings, and in particular the individual features thereof, may betaken independently or in any combination. That is, all embodimentsand/or features of any embodiment can be combined in any way and/orcombination, unless such features are incompatible. The applicantreserves the right to change any originally filed claim or file any newclaim accordingly, including the right to amend any originally filedclaim to depend from and/or incorporate any feature of any other claimalthough not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by wayof example only, with reference to the accompanying drawings, in which:

FIG. 1 illustrates an example of a vehicle;

FIG. 2 illustrates an example of a controller and an example of avehicle system;

FIG. 3 illustrates an example of a method; and

FIG. 4 illustrates an example of a user interface.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 illustrates an example of a vehicle 10 in which embodiments ofthe invention can be implemented. In some, but not necessarily allexamples, the vehicle 10 is a passenger vehicle, also referred to as apassenger car or as an automobile. Passenger vehicles generally havekerb weights of less than 5000 kg. In other examples, embodiments of theinvention can be implemented for other applications, such as industrialvehicles, air or marine vehicles.

The vehicle 10 of FIG. 1 comprises energy storage means 11 and atraction motor (not shown). The motor is configured to convert energystored within the energy storage means 11 into energy for providingtractive force for propelling the vehicle 10. In some, but notnecessarily all examples the energy storage means 11 is a tractionbattery (‘battery’ herein), and the motor is an electric motor. Thevehicle 10 may be an electric vehicle, i.e. a hybrid electric vehicle oran all-electric vehicle.

In some, but not necessarily all use cases based on the followingdisclosure there is provided a self-learning electric vehicle 10 featurewhich is designed to help a user when they find themselves in asituation with insufficient charge in their vehicle battery 11. Ahuman-machine interface output may provide several user-selectableoptions for enabling manual inputting of a requirement for futuredriving. The options may include: 1) giving the user enough change for‘n’ typical days of driving, where ‘n’ is a variable and the user canset ‘n’ to specify whether they want enough charge to only completetoday or the next three typical days, for example; 2) enough charge totravel ‘x’ typical units of distance (e.g. miles) in their vehicle,wherein ‘x’ can be set by the user to a desired distance; 3) enoughcharge to reach a user-selected location (e.g. destination); and 4)charging the battery 11 to ‘y’ % state of charge (SoC), wherein y can beset by the user. The feature determines a user's requirement based onuser selection of an option. Based on a learnt routine, the featureprovides an output informing the user that they will need to chargetheir vehicle 10 for a minimum of one hour to be able to complete theirtypical Monday driving, for example.

FIG. 2 illustrates an example controller 210 and an example vehiclesystem 330, configured to enable various aspects and embodiments of theinvention to be performed. It would be appreciated that otherarrangements from that of FIG. 2 are possible.

The vehicle system 330 comprises a plurality of subsystems and monitors,each of which is operably coupled with the controller 210. In someexamples, monitors may be implemented as control logic within thecontroller 210. Example subsystems and monitors, illustrated in FIG. 2,include:

-   -   A state of charge monitor 260, for providing data indicative of        a current state of charge of the battery 11. The state of charge        monitor 260 or the controller 210 may be configured to determine        a history of the state of charge of the battery 11. This        functionality could be embedded within a control module        integrated or associated with the battery 11, for example.    -   An optional key-on/key-off monitor 270, for providing data        indicative of whether the vehicle 10 is currently in a key-on or        in a key-off state. This functionality could be embedded within        a powertrain control unit, for example. In accordance with the        ordinary definitions of key-on and key-off, a vehicle 10        entering a key-on state means that a user has operated their        vehicle key such that the vehicle 10 is operable to produce        tractive force in response to depression of its accelerator        pedal or other suitable user interface means, such as a        twist-grip. A vehicle 10 entering a key-off state means that a        user has operated their vehicle key such that the vehicle 10 is        unable to produce tractive force in response to depression of        its accelerator pedal.    -   An optional user-selectable subsystem usage monitor 280, for        providing data indicative of which user-selectable        energy-consuming subsystems are in use and of the rate of energy        consumption of each user-selectable subsystem. Examples of        monitored user-selectable subsystems include an air conditioning        system, an informainment system, a vehicle interior lighting        system, etc. This functionality could be embedded within a        control unit receiving information from one or more power        consumption sensors associated with each of the user-selectable        subsystems, for example.    -   An optional navigation system 290, for providing data indicative        of one or more of: a current geographical location of the        vehicle 10; route information; points of interest such as        charging locations at which charging stations are located, etc.        The navigation system 290 may comprise a Global Positioning        System (GPS) or the like. The data indicative of charging        locations may be augmented with metadata indicating properties        of the charging station, such as a charge rate or compatibility        information. The controller 210 could be configured to retrieve        the metadata from one or more remote computing means, such as an        external server, in dependence on data from the navigation        system 290.    -   An output device 300. In some examples, the output device 300 is        configured to present an output to a user of the vehicle 10. The        output device 300 may be an audio output device and/or a visual        output device. In other examples, the output device 300 may not        be part of the vehicle system 330 and may instead be a portable        user device such as a mobile telephone, a so-called ‘smart’        watch, or similar portable media devices, able to communicate        with the controller 210 of the vehicle 10. This enables a        portable user device to present the output to the user, even if        the user is remote from the vehicle 10.    -   An optional input device 310 (e.g. button, touchscreen) for        enabling a user to make inputs in response to user-input prompts        presented by the output device 300. The input and output devices        may together form a human-machine interface 320.

The vehicle system 330 may comprise any one or more of the abovesubsystems, and other subsystems not in the above list operably coupledwith the controller 210. The controller 210 is configured to receive therespective data from and/or transmit commands to the subsystems of thevehicle system 330. In some examples, the controller 210 is embodiedwithin the vehicle 10 as part of the vehicle system. In other examples,the controller 210 is remote from the vehicle 10. The data can beexchanged one or more vehicle buses, such as via a Controller AreaNetwork (CAN) bus, and/or via an interface for vehicle-externalcommunication (e.g. wireless interface).

For purposes of this disclosure, it is to be understood thatcontroller(s) described herein can each comprise a control unit orcomputational device having one or more electronic processors. See forexample FIG. 2 which shows a control unit having an electronic processor220; and at least one electronic memory device 230 electrically coupledto the electronic processor 220 and having instructions 240 storedtherein. A vehicle 10 and/or a system thereof (such as the controller210) may comprise a single control unit or electronic controller oralternatively different functions of the controller(s) may be embodiedin, or hosted in, different control units or controllers. A set ofinstructions could be provided which, when executed, cause saidcontroller(s) or control unit(s) to implement the control techniquesdescribed herein (including the described method(s)). The set ofinstructions may be embedded in one or more electronic processors, oralternatively, the set of instructions could be provided as software tobe executed by one or more electronic processor(s). For example, a firstcontroller may be implemented in software run on one or more electronicprocessors, and one or more other controllers may also be implemented insoftware run on or more electronic processors, optionally the same oneor more processors as the first controller. It will be appreciated,however, that other arrangements are also useful, and therefore, thepresent disclosure is not intended to be limited to any particulararrangement. In any event, the set of instructions described above maybe embedded in a computer-readable storage medium (e.g., anon-transitory storage medium) that may comprise any mechanism forstoring information in a form readable by a machine or electronicprocessors/computational device, including, without limitation: amagnetic storage medium (e.g., floppy diskette); optical storage medium(e.g., CD-ROM); magneto optical storage medium; read only memory (ROM);random access memory (RAM); erasable programmable memory (e.g., EPROM adEEPROM); flash memory; or electrical or other types of medium forstoring such information/instructions.

Aspects and embodiments of the invention can alternatively be embodiedas computer program code 240 stored on a computer readable storagemedium 250, as also illustrated in FIG. 2.

FIG. 3 illustrates a method 30 for determining a charging requirementfor the battery 11 of the vehicle 10 described in relation to FIG. 1.The controller 210 of FIG. 2 may be configured to perform the method 30.

The method 30 comprises, at block 31, determining a routine of use ofcharge of the battery 11.

In some examples, determining a routine at block 31 comprisescontinually collecting data indicative of a current state of charge(SoC) of the battery 11 to determine a history of SoC. The controller210 could be configured to obtain such data from the state of chargemonitor 260, for example.

A “routine” refers to an established course of procedure, therefore thedata collection begins significantly earlier than a most-recent chargingevent of the battery 11. For example, the data collection may be‘cradle-to-grave’ data collection, i.e. may operate continually over thewhole lifespan of the vehicle 10.

A “routine” more specifically also refers to a repetitive procedure,therefore in one example determining the routine at block 31 maycomprise continuously collecting the data throughout a cycliccalendar-based routine. Data collection may be performed in accordancewith known machine learning techniques such as nearest neighbourregression and/or ensemble learning, for example, although other machinelearning techniques are envisaged. Each cycle for which the data iscollected increases the performance of any predictions made based on thedetermined routine, because the accuracy of an expected use of SoCmetric (e.g. average) and of an associated error/confidence score (e.g.variance) increases.

Regarding the time interval of the cyclic calendar-based routine,different users operate their vehicles according to different routines.A ‘weekly’ routine may be appropriate to those users who have similardriving patterns from one week to the next. A user whose driving habitsare determined by a fortnightly shift pattern for their place of workmay operate on a ‘fortnightly’ routine. Other time intervals include‘daily’ or ‘monthly’. In some examples, the state of charge data withrespect to a weekly routine may be at day-level granularity.

In some, but not necessarily all examples, the determined routine is, ineffect, a model of SoC over time from which predictions can be madeindefinitely into the future with a certain level of confidence,assuming of course that the conditions affecting the learning of theroutine do not radically change in the future (e.g. user changes job,moves house etc.).

In some, but not necessarily all examples, determining the routine atblock 31 further comprises determining a routine of usage ofuser-selectable energy-consuming vehicle subsystems, for example usingdata from the user-selectable subsystem usage monitor 280. This wouldenable the discrimination of energy consumption purely for producingtractive force from energy consumption for other purposes. Thisincreases predictive performance of any predictive model based on theroutine, because a prediction of SoC can then account for the likelihoodof use of user-selectable subsystems.

In some, but not necessarily all examples, determining the routine atblock 31 further comprises determining a routine of distance travelledby the vehicle 10, in dependence on continual monitoring of distancetravelled by the vehicle 10. This historic distance data enables aninternal prediction to be made of expected distance to be travelled in agiven day.

In some, but not necessarily all examples, algorithms for the routinedetermination are trainable. For example, the routine determinationcomprises weighting SoC data according to age, so that the average iscomputed based on weighted SoC data. Older SoC data may be given a lowerweight. This ensures that the determined routine quickly adjusts tochanges in the user's routine, for example when the user moves house,and even to changes of season, for example accounting for increased useof air conditioning.

In some, but not necessarily all examples, the controller 210 isconfigured to determine whether the vehicle 10 is being drivenout-of-routine. This determination can be made, for example, by makingan internal prediction of expected distance to be travelled in a givenday, using the historic distance data, and an internal prediction ofexpected SoC to be consumed in a given day. If on a given day, the usertravels significantly more than they are expected to travel, then theoutput device 300 prompts the user to confirm whether they are drivingout-of-routine. If the user confirms this with an input via the inputdevice 310, the data for that day is discarded. Discarded data is nottaken into account in updating the routine.

At block 32, the method 30 comprises determining a user requirement forfuture driving of the vehicle.

The user requirement may define a time period and/or distance of futuredriving of the vehicle 10 for which the energy storage means 11 must notbe in a charge-depleted state. This represents a constraint forbiddingthe battery 11 from reaching its charge-depleted state during a definedtime period and/or distance of future driving of the vehicle. The userrequirement may define a location (e.g. destination) to which thevehicle 10 is to be driven. Alternatively, the user requirement maydefine a distance by which the vehicle 10 is to be driven, such as 80miles. Alternatively, the user requirement may define a time for whichthe vehicle 10 is to be driven, such as “today”. The time may be atday-level granularity.

If the user requirement represents distance, this distance may becalculated from a location or a destination input by a user.

In some, but not necessarily all examples, the controller 210 uses datafrom the navigation system 290 to determine a distance, a locationand/or a route to the location.

In some examples, the user requirement is determined in response to amanual user selection of a charging option, as will be described laterin relation to FIG. 4. The user requirement may for example comprise amanually entered location, a distance or a time requirement.

Additionally or alternatively, the user requirement can be determinedbefore any user selection of a charging option is made. In other wordsthe user requirement could be determined predictively, in advance of anymanual user selection of a charging option such as that shown in FIG. 4.Such a prediction could be dependent on information recorded in theroutine or in conjunction with determining the routine, such as alocation (e.g. destination), a distance or a time requirement. As aresult of this prediction, it will be possible to display to the user anumber of charging options that are likely to be of interest to theuser, such as ‘Get home’, or ‘Fill up for the week’. Each option may bedisplayed concurrently with a time requirement for that option as willbe determined in block 37 below. Once the user has selected an option,the method may loop back to block 32 to the extent that the requirementindicated by their selection differs from a prediction and thereforerequires a recalculation of the minimum charging time.

At block 33, the method comprises predicting a reduction in the state ofcharge of the battery 11 associated with the user requirement independence on the determined routine.

In one example implementation, block 33 determines how much of thebattery's charge 11 will be consumed by the time the time period and/ordistance of future driving has been completed, assuming the vehicle isdriven according to the determined routine throughout the defined timeperiod and/or distance of future driving. This could be regarded as achange in SoC, or a ‘delta’.

For example, if the time period and/or distance of future drivingrelates to a time, block 33 may determine how much charge is expected tobe consumed when the required time (e.g. ‘today’) has elapsed, based onthe determined routine. For example, block 33 may reveal a usage of 10kWh for today.

If the time period and/or distance of future driving relates to alocation or distance, block 33 may determine how much charge is neededfor driving the distance needed in dependence on the determined routine.In some examples this relies on an estimation of charge usage per-unitdistance from the routine. Usage per-unit distance may in some examplesvary in the routine in dependence on time. To give an example, usage maybe 2kWh per mile in the summer and 1 kWh per mile in the winterdepending on ambient and road conditions.

At block 35, the method comprises determining a minimum SoC for thebattery 11 for enabling the user requirement to be satisfied independence on the predicted reduction of block 33.

In one implementation, block 35 comprises determining a current SoC,subtracting from the current SoC the delta determined at block 33 todetermine the resulting SoC, and determining whether the resulting SoCis below a threshold defining a charge-depleted state of the battery 11.

A charge-depleted state may refer to SoC being below a reserve level ofSoC (e.g. 25%), or being insufficient for driving a lower threshold ofdistance (e.g. 50 miles) or for a next journey. The battery 11 requirescharging when the battery 11 is in its charge-depleted state. In thecharge-depleted state the battery 11 may still be usable for providingtractive torque, but a warning may be output to the user via an outputdevice (e.g. 300) indicative of the charge-depleted state.

If the resulting SoC is expected to fall below the threshold by (orbefore) the end of the defined time period and/or distance of futuredriving, then the current SoC is below the minimum SoC needed tocomplete the defined time period and/or distance and the vehicle 10should be charged first. Otherwise, the current SoC is enough and thevehicle 10 will not need to be charged first.

The minimum SoC is no more than required for ensuring that the SoCremains above the threshold by (and optionally before) the end of thedefined time period and/or distance of future driving.

In some, but not necessarily all examples, the threshold for a depletedstate is adjustable. For example, the controller 210 could be configuredto set the reserve level in dependence on confidence/error (e.g.variance) metrics of the routine data. For example, if the user drivesto different locations every Saturday, the variance will be high forSaturday. The reserve level could be set to 20% for Saturdays. If theuser drives to the same locations at the same times every Friday, areserve level of 10% may be appropriate for Friday.

At block 37, the method 30 comprises providing an output to the userindicative of a time requirement for increasing the state of charge ofthe energy storage means to a value at (optionally above) the minimumstate of charge. If the controller 210 carrying out the method 30 doesnot itself comprise the output device 300, block 37 may consist oftransmitting information to the output device 300 to cause, at least inpart, the presentation of the above-mentioned output to the user.

The user can then see, from looking at the output device 300 or otherdisplay device displaying the output (and/or listening to an audiodevice, etc.), how long they should charge their vehicle 10 for at aminimum.

In some, but not necessarily all examples block 37 or blocks 32 to 37,is performed in response to a determination that the current SoC isinsufficient, i.e. the predicted reduction subtracted from a current SoCof the battery 11 indicates a charge-depleted state of the energystorage means. In some examples block 37 or blocks 32 to 37, may beperformed while the vehicle 10 is plugged in or otherwise coupled to acharging station, for example in response to detection of the vehicle 10being plugged in or otherwise coupled to a charging station. Such adetection may indicate an electrical coupling of the vehicle to acharging station.

In an example implementation, the output time requirement is indicativeof a time at which or how long until the state of charge of the energystorage means 11 is expected to be at the value. In an exampleimplementation, the output time requirement represents how long thevehicle will need to be plugged in or otherwise coupled to an energysource and charging for the current SoC to transition to the minimumSoC. The controller 210 could be configured to determine the timerequirement in dependence on determining how much charge is required toincrease charge from the current SoC to the required minimum SoC, anddetermining a rate of charging associated with a charger for the energystorage means.

In some examples, the controller 210 is configured to determine the rateof charge using deterministic properties by accessing informationindicating the rate of charge for a given battery 11 or charger of thebattery 11. The deterministic properties could be obtained from acontrol module integrated with the battery 11, from an external controlmodule implemented in a charging station, from an electronic memorydevice of the controller 210, or the like. In other examples, thecontroller 210 is configured to determine the rate of charge usingnon-deterministic properties, for example by interrogating the routinedetermined at block 31, and determining the typical rate of charge independence on past SoC with respect to time. For example, the routineindicates that an 80% SoC increase requires 8 hours of charging, so therate is 10% per hour.

In some, but not necessarily all examples, the above-mentioned output ofblock 37 can be presented on an output device 300 or as part of a systemof output devices that present additional useful information to theuser.

FIG. 4 shows an illustrative example of a user interface 40 thatpresents the output and other outputs as pre-charging messages. In FIG.4 but not necessarily in all examples, the user interface 40 is a humanmachine interface 320 that presents to the user a plurality of optionsfor charging their vehicle battery 11. The options are individuallyuser-selectable via the input device 310, enabling the user to select acharging option. In some examples, the user interface 40 is displayed inresponse to detection of the vehicle 10 being plugged in or otherwisecoupled to a charging station. In some, but not necessarily allexamples, performing block 37 comprises displaying the user interface40.

A first displayed option 41 is an output calculated from blocks 31-37,based on a user requirement for driving to the destination ‘home’. Atime requirement of one hour is displayed in conjunction with the firstoption, indicating that one hour of charging is needed for getting home.

A second displayed option 42 is a further output calculated from blocks31-37, based on a user requirement for a week's worth of charge. A timerequirement of six hours is displayed in conjunction with the secondoption, indicating that six hours of charging is needed for a week'sworth of charge. The user may be able to set a variable ‘n’ indicatinghow many days of charge are needed, ranging from ‘today’ to a week orbeyond.

A third displayed option 43 is a further output calculated from blocks31-37, based on a user requirement for 50 miles (approximately 80 km)worth of charge. A time requirement of three hours is displayed inconjunction with the third option, indicating that three hours ofcharging is needed for 50 miles worth of charge. The user may be able toset a variable ‘x’ indicating how many units of distance (e.g. miles)are needed.

A fourth displayed option 44 is a required state of charge output thatprovides the user with the option of charging to a user-specifieddesired SoC, should none of the options calculated from blocks 31-37 beappropriate to the user's current context. Other options based ondifferent (second, third etc.) user requirements may be provided invarious examples, not limited to the above options. The user may be ableto set a variable ‘y’ indicating how much SoC is needed.

In some, but not necessarily all examples, the output of block 37 isinstead a post-charging message indicating that the SoC of the battery11 is at the value, i.e. the SoC has transitioned from being below thevalue to being the value. Such an output is indicative of a timerequirement for increasing the state of charge of the energy storagemeans to a value at or above the minimum state of charge, to the extentthat the time requirement is now zero, i.e. the battery 11 now has theminimum SoC for achieving the user requirement for future driving of thevehicle 10.

The output 37 in the form of a post-charging message could represent aprompt for the user to return to their vehicle which is now ready todrive. In some examples, the post-charging message is transmitted via alocal and/or wide area network to a portable user device of the user, sothat the user can feel free to leave their vehicle 10 during chargingand still be able to finish charging at the earliest possible time, dueto the prompt.

The method 30 includes an optional block 39 (marked by dashed lines),which occurs after block 37 if the output of block 37 is a pre-chargingmessage, and before block 37 if the output of block 37 is apost-charging message. Block 39 comprises charging of the energy storagemeans to the value, in dependence on receiving a user confirmationinput. If the controller 210 carrying out the method 30 does not itselfcomprise the means for charging the energy storage means, charging theenergy storage means refers to transmitting information to the means forcharging the energy storage means to cause, at least in part, thecharging to occur.

The user confirmation input may be an input, optionally provided via thehuman machine interface 320, specifying a charging option such as one ofthe options described in relation to FIG. 4, or otherwise confirmingthat the time requirement provided in relation to block 37 isacceptable. If multiple outputs are provided, the input specifies whichof those outputs has been selected by the user.

The blocks illustrated in FIG. 3 may represent steps in a method and/orsections of code in the computer program 240. The illustration of aparticular order to the blocks does not necessarily imply that there isa required or preferred order for the blocks and the order andarrangement of the block may be varied. Furthermore, it may be possiblefor some steps to be omitted.

Although embodiments of the present invention have been described in thepreceding paragraphs with reference to various examples, it should beappreciated that modifications to the examples given can be made withoutdeparting from the scope of the invention as claimed. For example theenergy storage means could be other than a traction battery 11 for anelectric vehicle. References to a state of charge/charge could bereferences to the quantity of energy stored in the energy storage meansfor conversion into torque for producing tractive force.

Features described in the preceding description may be used incombinations other than the combinations explicitly described.

Although functions have been described with reference to certainfeatures, those functions may be performable by other features whetherdescribed or not.

Although features have been described with reference to certainembodiments, those features may also be present in other embodimentswhether described or not.

Whilst endeavoring in the foregoing specification to draw attention tothose features of the invention believed to be of particular importanceit should be understood that the Applicant claims protection in respectof any patentable feature or combination of features hereinbeforereferred to and/or shown in the drawings whether or not particularemphasis has been placed thereon.

1. A method for determining a minimum state of charge for a traction battery of a vehicle, the method comprising: determining a routine of use of charge of the traction battery; determining a user requirement for future driving of the vehicle; predicting a reduction in the state of charge of the traction battery associated with the user requirement based on the determined routine; determining a minimum state of charge for the traction battery for enabling the user requirement to be satisfied based on the predicted reduction; providing an output to the user indicative of a time requirement for increasing the state of charge of the traction battery to a value at or above the determined minimum state of charge; determining a second user requirement for future driving of the vehicle, and for the second user requirement: predicting a reduction in the state of charge of the traction battery associated with the second user requirement based on the determined routine; determining a second minimum state of charge for the traction battery for enabling the second user requirement to be satisfied based on the predicted reduction; and providing a second output to the user indicative of a time required for increasing the state of charge of the traction battery to a value at or above the second minimum state of charge, wherein the output and the second output are provided together and are each user-selectable, enabling charging of the traction battery to the corresponding value to be performed when selected.
 2. The method as claimed in claim 1, wherein the user requirement defines either or both a time period and a distance of future driving of the vehicle for which the traction battery must not be in a charge-depleted state.
 3. The method as claimed in claim 1, wherein the user requirement defines one or more of the following: a location; a distance; and a time period.
 4. The method as claimed in claim 1, further comprising charging the traction battery to the value based on receiving a user confirmation input.
 5. The method as claimed in claim 1, further comprising providing a required state of charge output prompting the user to input a value of a required state of charge of the traction battery, wherein the required state of charge output and the output are provided together and are each user-selectable, enabling charging of the traction battery to the corresponding value to be performed when selected.
 6. The method as claimed in claim 1, further comprising providing the output while the vehicle is plugged in or otherwise coupled to a charging station.
 7. The method as claimed in claim 1, wherein the time requirement is indicative of either or both a time at which or how long until the state of charge of the traction battery is expected to be at the value.
 8. The method as claimed in claim 1, further comprising: determining a rate of charge associated with a charger for the traction battery; and determining the time requirement based on the determined rate of charge.
 9. The method as claimed in claim 1, wherein the output comprises a post-charging message indicating that the state of charge of the traction battery is at the value.
 10. The method as claimed in claim 1, wherein the routine is determined using measurements of the state of charge of the traction battery recorded with respect to a cyclic calendar-based time interval.
 11. A controller comprising at least one electronic processor and at least one electronic memory device electrically coupled with the electronic processor and having instructions stored therein, the at least one electronic memory device and the instructions configured to, with the at least one electronic processor, cause a vehicle system to perform a method for determining a minimum state of charge for a traction battery of a vehicle, the method comprising: determining a routine of use of charge of the traction battery; determining a user requirement for future driving of the vehicle; predicting a reduction in the state of charge of the traction battery associated with the user requirement based on the determined routine; determining a minimum state of charge for the traction battery for enabling the user requirement to be satisfied based on the predicted reduction; providing an output to the user indicative of a time requirement for increasing the state of charge of the traction battery to a value at or above the determined minimum state of charge; determining a second user requirement for future driving of the vehicle, and for the second user requirement: predicting a reduction in the state of charge of the traction battery associated with the second user requirement based on the determined routine; determining a second minimum state of charge for the traction battery for enabling the second user requirement to be satisfied based on the predicted reduction; and providing a second output to the user indicative of a time required for increasing the state of charge of the traction battery to a value at or above the second minimum state of charge, wherein the output and the second output are provided together and are each user-selectable, enabling charging of the traction battery to the corresponding value to be performed when selected.
 12. The controller as claimed in claim 11, wherein the electronic memory device comprises a non-transitory computer readable medium having said instructions stored therein.
 13. The controller as claimed in claim 11, the method further comprising providing a required state of charge output prompting the user to input a value of a required state of charge of the traction battery, wherein the required state of charge output and the output are provided together and are each user-selectable, enabling charging of the traction battery to the corresponding value to be performed when selected.
 14. The controller as claimed in claim 11, the method further comprising providing the output while the vehicle is plugged in or otherwise coupled to a charging station.
 15. The controller as claimed in claim 11, wherein the time requirement is indicative of either or both a time at which or how long until the state of charge of the traction battery is expected to be at the value.
 16. The controller as claimed in claim 11, the method further comprising: determining a rate of charge associated with a charger for the traction battery; and determining the time requirement based on the determined rate of charge.
 17. The controller as claimed in claim 11, wherein the output comprises a post-charging message indicating that the state of charge of the traction battery is at the value.
 18. The controller as claimed in claim 11, wherein the routine is determined using measurements of the state of charge of the traction battery recorded with respect to a cyclic calendar-based time interval.
 19. A vehicle comprising a controller and at least one output device, the controller comprising at least one electronic processor and at least one electronic memory device electrically coupled with the electronic processor and having instructions stored therein, the at least one electronic memory device and the instructions configured to, with the at least one electronic processor, cause a vehicle system to perform a method for determining a minimum state of charge for a traction battery of the vehicle, the method comprising: determining a routine of use of charge of the traction battery; determining a user requirement for future driving of the vehicle; predicting a reduction in the state of charge of the traction battery associated with the user requirement based on the determined routine; determining a minimum state of charge for the traction battery for enabling the user requirement to be satisfied based on the predicted reduction; providing an output to the user indicative of a time requirement for increasing the state of charge of the traction battery to a value at or above the determined minimum state of charge; determining a second user requirement for future driving of the vehicle, and for the second user requirement: predicting a reduction in the state of charge of the traction battery associated with the second user requirement based on the determined routine; determining a second minimum state of charge for the traction battery for enabling the second user requirement to be satisfied based on the predicted reduction; and providing a second output to the user indicative of a time required for increasing the state of charge of the traction battery to a value at or above the second minimum state of charge, wherein the output and the second output are provided together and are each user-selectable, enabling charging of the traction battery to the corresponding value to be performed when selected, and wherein the output device is configured to receive the provided output and the second output, and to present the output and the second output to a user.
 20. The vehicle as claimed in claim 19, wherein the electronic memory device comprises a non-transitory computer readable medium having said instructions stored therein. 